The FBI has admitted to gathering secret intelligence about the annual Burning Man festival since 2010.

In response to a request under the 2012 Freedom of Information Act, the security service said its Special Events Management unit has kept files on festival-goers, known as ‘burners’ – to ‘aid in the prevention of terrorist activites and intelligence collection’.

But the FBI’s 16-page response to the question by Inkoo Kang is heavily redacted, with information about the technology being used to secretly gather the information being blanked out.